1. Field of the Invention
The present invention relates to a tilt control method, particularly for self-leveling construction lasers with tilt sensors such as tubular spirit levels based on gravitational force.
2. Description of the Prior Art
Tilt generally denotes an inclined position or deviation of an object from the normal position of rest or equilibrium which is determined by the acceleration due to gravity. Below, the use of a liquid level which, without limiting the subject matter, will be described more fully as an example of tilt sensors based on gravitational force.
The liquid level (tubular spirit level, spherical spirit level) that is commonly used in measurement technique is a hollow glass body or hollow plastic body filled with a liquid and a gas bubble. The hollow space in which the liquid and gas bubble are located is slightly curved with a defined radius on the upper side so that the gas bubble always floats to the highest point. Electronic spirit levels are tilt sensors which are based on gravitational force and which gauge the tilt measurements electrically or electro-optically. The measurement function of the tilt measurements is usually strictly linear to the tilt angle, and the rise of the measurement function is the sensitivity.
For a variety of reasons, actual electronic spirit levels can have inaccuracies and malfunctions which overlap, e.g., hysteresis effect in the movement of the gas bubble or in the electronic measurement detection, change in curvature of the hollow space, or accumulation of dirt particles at the hollow space, temperature-related expansion of the gas bubble, loss of liquid over time, and so on. When used for its prescribed purpose, an electronic spirit level for automatic tilt control of a tilt device with a tilt control algorithm that forms a control loop with a tilt control device that is controlled by this algorithm, is additionally subjected to the hysteresis effects and nonlinearities of both the tilt control device and the tilt control algorithm.
Particularly in self-leveling construction lasers, e.g., according to EP1524495, the accuracy and reliability of the automatically adjusted tilt of projected beams or planes should meet strict requirements and must also be sufficiently robust under the harsh environmental conditions common in the building industry.
According to EP0126083, a tilt monitoring and alarm system has a tubular spirit level with measurement based on capacitance. For preventing false alarms, a threshold detector forms hysteresis in the measurement arm.
According to WO0128820, a tilt sensor for vehicles, which is based on tubular spirit levels, is connected to a microcontroller which calculates the tilt and the acceleration from the detected position of the gas bubble using an algorithm.
An object of the present invention is to increase the reliability of tilt control methods with tilt sensors based on gravitational force.